Get in the game! Do your share in doubles.
As I see it:
While taking a lesson, a student queried me: “where should I stand in doubles.” At the same time demonstrating to me that, he stands about three feet from the net, and straddles the Singles sideline to prevent his opponents from hitting down the line.
He suggested “…by standing in the alley, no one could pass him down the line. True!
He also offered that his position gave his serving partner more room in which to hit their serve. Also true! I volunteered.
I agreed his reasoning made sense to protect the alley, and to give his serving partner room in which to place their serve was sound and purposeful; however, the execution and performance of this stratagem was flawed for “winning doubles” for several reasons. Let me explain.
Certainly, standing in the alley would discourage the down the line shot, but it’s not doubles in tennis; you leave so much territory uncovered, or to be covered by your partner. Not a good idea.
In doubles each team must decide how to adequately cover the entire court, where a tennis ball might land without leaving certain areas vulnerable, and open to your opponent.
Dividing the court equally and at the same time moving in tandem, wherever your partner might wander permits the easy, and adequate means to defend your side of the court. At the same time this makes it harder for your opponents to penetrate. The need to take the net, as soon as possible, and at all cost, cannot be overemphasized.
On certain points you might feign forgetfulness about watching the alley, just to entice an unwary opponent to present you with an easy “diagonally crosscourt” volley; just as you would move to one side of the service area, when waiting for the serve.
This trick is employed to invite your serving team to serve to a certain side of the court or to an opponents’ forehand, or backhand.
Standing to one side in order to protect the alley requires your partner to cover more than their share of the court because more of the court is exposed, thus standing in the alley to protect it should be avoided. Doing so immediately identifies your knowledge of the game of tennis to be weak.
Since your opponents’ strokes will be coming towards you, my experience shows me that by standing back at the service line when my partner is serving permits me more reaction time if the receiver is able to nail the serve.
And, being back from the net discourages lobs over my head, while also giving my partner all the court they need to see to serve into, so don't just stand on the sidelines, get on the court and into the games.